Relief mechanism for piston-valves.



No. 655,080. Patented July 31,1900.

a. n. HENDERSON. RELIEF MECHANISM FOR PISTON VALVES.

(Application flledvJan. 11, 1899.) (No Model.) 2 Sheets-Sheet l No.655,080. Patented July .31, I900.

Gm. HENDERSON.

RELIEF MECHANISM FOR PISTON VALVES.

(Application filed Jan. 11, 1899.)

(No Model.) 2 Sheets-Sheet 2.

N-ITED STATES PATENT Orr-Ion.

cnonenn. HENDEnson, oFRo'ANoKE, VIRGINIA.

RELIEF MECHANISM FOR PISTON-VALVES.

SPECIFICATION forming part of Letters Patent No. 655,080, dated July 31,1900.

. Application filed January 11, 1899. Serial No. 701,839. (No model.)

To aZZ whom it 1 7tcty c07c ce7nr V Be it known that I, GEORGE E.HENDERSON, a citizen of the United States, and a resident of Roanoke,Virginia, have invented certain.

Improvements in Relief Mechanism for Piston-Valves, of which thefollowing is a specification. r

The object of my invention is to provide means for automaticallyrelieving the piston- Valve of a locomotive or other engine of excessive back pressure, due to compression of water or steam in thecylinder of the engine of the locomotive.

Piston-valves, owing to the nature of their construction, are not ableto relieve themselves the same as a' slide or D valve. The slide-valvewill be raised from its seat by the excessive back pressure in thecylinder, thus relieving the pressure. Safety-valves have been providedon the cylinder-heads'for the purpose of relieving back pressure in the10- comotive using a piston valve, but these safety-valves have provedunsatisfactory.

In the accompanying drawings, Figure 1 is a sectional view through onecylinder and valve on the line 1 1, Fig. 3. Fig. 2 is a section on theline 2 2, Fig. 3. Fig. 3 is a sectional plan view on the line 3 3, Fig.1; and Fig. 4 is an enlarged sectional view of a portion of Fig. 2,illustrating more clearly my invention.

In the drawings I have shown simply one cylinder-casting of a locomotiveof the ordinary piston-valve type. The cylinder-casting on the oppositeside will be a duplicate of the one shown.

A is the cylinder-casting, having the cylinder 13, the valve-chamber O,and the steaminlet passage a and passages Z) b, one communicating withone end of the cylinder and the other with the opposite end. cis theexhaustpassage communicating with the ports at each end of thevalve-casing.

Ihave omitted the piston and its rod as well as the valve, as theseparts form no part of my present invention and are of the constructionordinarily used in this type of engine.

Steam is admitted from .the boiler through the central live-steampassage at to a passage 1) and into one end of the cylinder, while thesteam is exhausting from the opposite end of the cylinder through theother passage 12 to the exhaustpassage 0, and when the valve is movedinto the opposite position the passage of the steam and exhaust arereversed.

In the cylinder-casting A are two partitions A, forming a cavity adirectly under each passage Z), communicating with the cylinder. Screwedinto the partition is a valve-seat d, and adapted to the seat is acheck-valve D. When the valve is opened, the passage 1) communicateswith the passage ct through the cavity a; butthe check-valve is on theunder side of the partition, and consequently will close with pressurein the live-steam passage a, so that the valve is normally closed whenthe throttle-valve of the engine is opened; but when the locomotive isstanding and the live-steam passage a is free of steam under passages 19should be increased either by undue compression or by water in thecylinder above the steam-pressure in the passage a, the valve D will beforced from its seat and the pressure in the passage 1) will beinstantly relieved, thus preventing breaking or damaging thecylinder-head or piston.

While the above is the main feature of my invention and the point whichthe invention is intended primarily to cover, yet it affords theadvantage of allowing the locomotive to drift without creating a vacuumin the steamchest. When steam is cut oif, both checkvalves D D willremain open and the air can be forced from one end of the cylinder tothe other through the valves. Further, this construction will preventlocomotives from starting owing to the leaky throttle, as the steam asit slowly escapes will pass around the valves D D and into the passageZ) to the exhaust-passage 0.

Referring to Fig. 4, directly under the valve is a screw-cap-d. Onremoving thisscrew cap the valve and the valve-seat can be removed.

While I prefer to place the valves in the particular position shown,they can be placed at any point in the partition between the live;

steam passage or and the cylinder-passages b b, as in some types ofengines it may not be convenient to place the valves in the positionshown in the drawings. If the valve is placed without departing from'the main feature of my invention.

y ;I claim-as myinvent-ion- 1. The combination of a cylinder, acylindricalvalve-casing, a central steam-inlet passage,sidecylinder-passages and end exhaustpassages,cavities extendingfrom the livesteam passage under the cylindenpassages, ports in thepartition between the cavities and the cylinder-passages, a check-valvein each-port normally open but closing against steam-pressure in thelive-steam passage and opening against said steam-pressure when there isexcessive back pressure in one or other of the cylinder-passages,substantially as described.

2. The combination in a locomotive, of a steam-cylinder; a cylindricalvalve-chest,

live-steam and exhaust passages'lea'ding to said 'valve-c'h'es't andports leading to the steam-cylinder, a chamber to one side and'belowsaid valve-chest communicating with the live-steam passages, twocheck-yalves in the ;partition.between the saidchamber and thesteam-ports of the cylinder, said valves being normall-yheld-open bygravity, substantially as described.

The combination'in a locomotive-cylim .dercasting, of a steam-cylinder,a cylindrical val ve-chest, passagesleadin g fro m said valve- "chest"to-the steam' cylinder, to the exhaust and to the live-steam supply, apartition forming with the walls of the cylinder a-chamber communicatingwith the live-steam passages, and check-valves with valve-seats in saidpartition opening into the passages tothe-steamcylinder, threadedopenings in the lower wall of said ohamberdirectly beneaththe'checkvalves through which both valves and seats may be introducedand fitted in place and threaded plugs constructed toclose saidopenings, said valves and threaded openings being inside of thelocomotive-frame and so placed as to be readily accessible,substantially as described.

In testimony whereof I have signed my name to this specification in thepresence of two subscribing witnesses.

GEORGE R. HENDERSON.

' Witnesses:

R. H. PERsrNeER, JNo. A. PILOHER.

